I’m pretty sure it is as well. @noahl I suspect you may have missed this because you aren’t the one creating the topics.
Circling back to the email notification, and the approach to solved as a whole, I stumbled across this quote from Sam as part of my search:
I share both of these views. I would even go further and say marking the problem as solved is most valuable when the Topic is two or more pages(~6 posts) long. For shorter Topics the user is likely to scroll through each post anyway and make the judgement for themselves.
This sounds pretty good in terms of member contribution. It looks like the issue might be that the quantity marked as solved overall is low, rather than just the ratio.
Have you considered once a month/week, going through the list of unsolved topics and reaching out to the owners privately? The other question is, how useful is it to rely on the user’s contribution for this? In other words, is this user going to come back and ask 10 more questions, or are they only here for the one question and then leaving?